Field of the Invention
The present invention relates to an ink, an ink cartridge, and an image recording method.
Description of the Related Art
An inkjet recording method is one of the image recording methods that have been significantly developing in recent years because a high-quality color image can be easily recorded by the method despite the fact that its principle is simple. In addition, the method has rapidly become widespread not only in the image recording of a document, a photograph, and the like in households that has heretofore been mainstream but also in offices and industrial applications.
In the case of a printer for a household or for an office, printing is performed by scanning the recording surface of a recording medium with a short serial type head a plurality of times, and hence a printing speed is limited. Meanwhile, a long line type head has been developed in recent years. When a recording apparatus, such as a printer, mounted with such line type head is used, an image of a size corresponding to a head width can be recorded by one scan (one pass). Accordingly, the inkjet recording method has started to be adopted also in a commercial printing industry where printing at higher speed is required.
In the commercial printing industry, it is necessary that a large amount of images can be printed at lower cost. Accordingly, it has been desired that a high-quality image can be recorded also on inexpensive and thin paper that has been generally called printing paper and has been widely used. However, in the case of paper classified as woodfree paper or fine coating paper, an ink is liable to permeate into the paper and hence its strike-through is liable to be conspicuous. Accordingly, in the commercial printing industry where duplex printing is often performed, it has been a large challenge to record a high-quality image at high speed while suppressing the strike-through to the extent possible.
The simplest method of suppressing the strike-through is a method involving reducing the ejection amount of the ink per unit area of a recording medium (paper). However, the reduction in ejection amount of the ink makes it difficult to completely conceal the surface of the paper, and is hence liable to cause a problem, such as the occurrence of a stripe in a solid image. In the case of a pigment ink to be frequently used in commercial printing, a dot diameter after printing is liable to be smaller than that of a dye ink. Accordingly, a reduction in ejection amount of the pigment ink more remarkably causes a problem, such as the occurrence of a stripe in a solid image.
A method for the suppression of strike-through and the occurrence of a stripe is a method involving increasing the ejection amount of an ink to forcibly expand a dot diameter to suppress the permeation of the ink after its impingement into a recording medium. For example, the following image recording method has been proposed (Japanese Patent Application Laid-Open No. 2009-226850). A treatment liquid containing a component for aggregating a pigment in an ink (aggregation component) is applied to a recording medium in advance, and the permeation of the ink into the recording medium is suppressed by causing the ink after its impingement and the aggregation component to react with each other. In addition, an ink set containing an ink having the following feature has been proposed (Japanese Patent Application Laid-Open No. 2011-127001). The ink is increased in surface tension so that its permeation into a recording medium may be suppressed, and hence its strike-through can be reduced.